Microorganisms as driving factors for the community structure of testate amoebae along an altitudinal transect in tropical mountain rain forests

We investigated microbial biomass, fungal biomass and microbial community structure at three altitudes (1000, 2000 and 3000 m) and in two soil layers [L/F layer (Layer I) and underlying H/Ah layer (Layer II)] of tropical mountain rain forests in southern Ecuador. Basal respiration, microbial biomass and concentration of ergosterol generally declined from Layer I to Layer II and peaked at 2000 m. Compared to temperate forest ecosystems microbial biomass and ergosterol concentrations were generally low. Patterns in phospholipid fatty acids indicated that the composition of microbial communities markedly changed from Layer I to Layer II. These differences between layers decreased with increasing altitude. The concentration of the arbuscular mycorrhizal fungal marker PLFA 16:1ω5c decreased with altitude in Layer I but increased in Layer II. The fungal-to-bacterial ratio increased with altitude and was higher in Layer I than in Layer II. Presumably, low microbial biomass in soils of tropical forest ecosystems is due to high temperature associated with high respiration but also low litter quality, with the latter declining with altitude. These conclusions are supported by the fact that at higher altitude the microbial community changed from a bacterial-dominated to a fungal-dominated system. CCA showed that microbial biomass correlated closely with density of a number of putatively bacterial feeding testate amoeba species including Corythion dubium Taranek, 1871, Euglypha cristata Leidy, 1879, Trigonopyxis arcula Penard, 1912, Tracheleuglypha dentata Deflandre, 1928 and Trinema lineare Penard, 1890. Ergosterol concentrations, but not the PLFA 18:2ω6c, strongly correlated with the putatively fungal feeding species Phryganella acropodia (Hertwig, Lesser, 1874) Hopkinson, 1909. Generally, parallel to microbial biomass and ergosterol concentrations the density of testate amoebae peaked at 2000 m. However, compared to microbial parameters changes in testate amoebae communities between two layers were less pronounced. The data suggest that density and community structure of testate amoebae are driven by the availability of food resources (bacteria and fungi) which at high altitude decrease with increasing moisture and decreasing pH.     

Spectral light-reflection data dimensionality reduction for timely detection of yellow rust

Precision Agriculture - Yellow rust (YR) wheat disease is one of the major threats to worldwide wheat production, and it often spreads rapidly to new and unexpected geographic locations. To cope...     

Testate amoebae (protista) of an elevational gradient in the tropical mountain rain forest of Ecuador

We investigated the species composition of testate amoebae at three altitudes (1000, 2000 and 3000 m) and two horizons (L and F/H/Ah) of a tropical mountain rain forest in southern Ecuador. A total of 135 species and intraspecific taxa of testate amoebae were found (36 samples). Rarefaction plots suggest that only few more species are to be expected. Species number in the L horizon was at a maximum at 2000 m (109 species) and similar at 1000 and 3000 m (75 and 71 species, respectively). Species numbers in the F/H/Ah horizon were 29, 67 and 48 at 1000, 2000 and 3000 m, respectively. The density of testate amoebae in the L horizon increased significantly in the order 1000<3000<2000 m with 3147±129, 9198±144 and 12,497±1317 ind. g⁻¹ dry matter and in the F/H/Ah horizon with 176±25, 3118±97 and 4986±102 ind. g⁻¹ dry matter, respectively. The significant Horizon×Elevation interaction reflects the exceptionally low abundance of testate amoebae in the Ah horizon at 1000 m. The results suggest that species richness of testate amoebae does not decrease continuously with elevation; rather, it peaks at an intermediate elevation. Further, the data suggest that diversity, but not density of testate amoebae in tropical forests exceeds that in temperate forests. Morphological features of testate amoebae reflected semiaquatic habitat conditions. The great majority of testate amoebae species of the studied tropical mountain rain forests are geographically widespread, including temperate regions; however 9 of the species (i.e. 6.7%) are considered tropical, some of these species likely represent Gondwana relicts.